It is proposed that previous studies of the radiation chemistry of DNA dinucleoside monophosphates be extended to tetramers. Future work would have two principal objectives: (1) To examine the effect of specific radiation induced lesions on the conformation and function of these DNA model compounds particularly base pairing. This aspect of the investigation would involve NMR studies of d(CGTA)*/d(TACG) and d(CGTA)/d(TACG)* duplexes where the asterisk indicates a tetramer bearing a modified nucleotide. (2) To utilize DNA tetramers bearing a specific radiation-induced lesion to isolate and characterize the 3' and 5' nucleotides having the lesion. These modified nucleotides will serve in the isolation of the same lesion from polymer DNA. The ultimate objective of the research is to be able to detect and quantitate specific lesions in the DNA taken from organisms exposed to ionizing radiation under various conditions.